Electrical conductor



Jan. 19, 1932. B. s. LESLIE 1,841,447

ELECTRICAL CONDUCTOR Filed Aug. 14, 1925 /NVENT R- Patented Jan. 19, 1932 UNITED STATES PATENT OFFICE BERNARD' S. LESLIE, OF BEVERLY, MASSACHUSETTS, ASSIGNOB. TO UNITED SHOE MA- GHINERY CORPORATION, `OF PATERSON, NEW JERSEY, A CORPORATION OF NEW JERSEY ELECTRICAL ooNnUcfron i Application med August 14, 1925. Serial No. 50,231.

The present invention relates to improved methods for anchoring insulated electrical conductors and is herein disclosed by way of illustration with reference to a thermal unit for use in heating tools and implements of various sorts such, for example, as those employed in performing finishing and burnishing operations on boots and shoes. It will. be understood, however, that in various aspects the invention is not restricted to such use. A

According to the practice generally employed today, insulated conductors are anchored by terminating the insulation above the extremity of the conductor and securing the exposed end of the conductor to the electrical unit in any suitable manner as, for example, by means of binding posts, soldering, etc. When this method is used. the resulting connection is apt to be unsatisfactory and objectionable since it leaves exposed the terminals of the conductors with a resulting liability of short circuiting the thermal unit through contact of the terminals with each other or throu h the collection of grease and dust between t e terminals; or of grounding through contact of the terminals with the metal casing of the unit or with the machine in which it is used. A further objectionable feature of this means of connecting or anchoring the conductors consists in the fact that the unit upon which the connection is employed is often one which has to be inserted into a socket or extractediherefrom by a thrust or pull exerted on the insulated conductors which will tend to break the wires at the connection. Furthermore, when the connection is em loyed ina thermal unit, the heat generate by the unit causes charring of the exposed ends of the insulation which tends to fray the insulation and to expose a greater .portion of the electrical conductor than is ordinarily ex osed, thereby increasing the dangers alrea y spoken of in this paragraph. In order to guard against these dangers, the connections are often wrapped with ta e or some similar material. The lasting qua ities of the tape are, however, unsatisfactory and as a result the tape hardens and cracks or becomes unwound.

In view of the foregoing, the present invention has for an object the provision of improved insulatin and connecting means that will obviate ythe angers of grounding, shortcircuiting, and charring, and will further provide a rigid-connection of considerable strength by which the unit may be inserted into or extracted from a socket or cavity without straining the wires.

Theinvention provides an improved method of producing an insulated connection and, as herein exemplified, comprises surroundin the conductors with an insulatingmateria impregnating the insulation with a heat-resisting material, baking the insulating conductors so treated, and anchoring the extremities of the insulation in a mold Aof heat-resisting material.

The invention is more full described in the following specification an illustrated in the accompanying drawing, which shows a thermal unit constructed in accordance with the invention, the unit being inserted into a socket or cavity.

The unit shown comprises a body portion having a cylindrical casing 2 containing a resistance coil of the ordinary type and having an open end 4 from which projects a porcelain plug 6. This plug 6 serves as an insulator for conductors 8 and 10 which extend through the plug and into the casing of the unit and are connected to the resistance coil.

As illustrated, the unit iscontained within a socket or cavity 12 located within a tool or machine 14 which it is proposed to heat. The open extremity of the socket is covered by a protection plate 16 to prevent grease and dust from collecting in thesocket and the conductors are led through the late 16 by means of a conduit 18 and a c amping elbow 20. Insulation 22 of woven asbestos or any other suitable heat-resisting material having a high permeability to liquid insulators surrounds the conductors 8, 10 and terminates in proximity to the porcelaln plug 6, as illustrated.

. So much of the description as has already been given is characteristic of the faulty method heretofore generally employed in securing conductor terminals to electrical units, which is subject to the objections and dangers referred to in an earlier paragraph.

socket. It will be apparent that the pressure or tension brought to bear upon the connection between the conductors and the unit will exert a strong tendency to break or weaken the conductors.

To obviate these objections, the illustrated insulation is thoroughly impregnated with a heat-resisting solution such, for example, as Bakelite varnish` and after removing the surplus varnish by washing the insulating sleeve with alcohol or soapy water, or in any other suitable manner, the impregnated article is treated to a baking operation in order to increase the durability of the insulation while at the same time rendering it substantially rigid and non-elastic.

To the same end, the illustrated casing 2 is extended (by means of a sleeve as illustrated) at 26 to surround completely and to extend substantially beyond the porcelain projection 6. rihe conductors extend down through the sleeve 26 and into the body of the unit and the insulation sleeves 22 surrounding the conductors also lead a substantial distance into the sleeve 26. After this connection has been made, the sleeve or mold 26 is filled with an insulating paste (indicated at 28) made from a solution of heatresisting material having a. high dielectric constant such, for example, as Bakelite varnish mixed with magnesium or any other suitable binder. This paste is firmly pushed into the mold 26 to occupy all the space surrounding the conductors and their insulation sleeves. In order to cause setting of this paste seal, the paste is submitted to a baking operation. This, of course, may be accomplished by put-ting the article in an oven at the proper temperature. Applicant has found, however, that a satisfactory and more economical and convenient method of performing this operation is by connecting the electrical unit with a suitable supply of current and allowing the hea-t generated by the unit to perform the baking operation. This second baking operation results in a fusion between the material with which the insulation has been impregnated and the heat-resisting material located within the mold, and cements the conductors and the sleeve 26 to the material in the mold, thereby producing an air-tight,

rigid connection between the insulators, the conductors and the electrical unit. Such a connection prevents an possible Contact between the conductors t emselves or between either conductorand a metal portion of the casing or mold.

The Bakelite in the insulation coalesces with the Bakelite comprising a body portion 28 having integral sleeves surroundlng the conductors 8, 10, in which the fibers of the insulating fabric 22 are individually embedded.

Having thus describedmy invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. That improvement in the art of insulating exposed connections between electrical conductors and electrical units whichconsists in surrounding the exposed connection with an infusible material and passing electric current through the conductors to heat the unit and thereby to bake the heat-resisting material in order to produce a rigid insulation.

2. rihat improvement in the art of anchoring the extremities of insulation which consists in impregnating the insulation with a phenol condensation product solution, baking the impregnated insulation and then embedding it in a molded member of infusible material, and submitting the embedded insulation to a baking operation to cause fusion between the impregnating material in the insulltor and the bed of heat-resisting materia 3. That improvement in the art of anchor- BERNARD s. Lastre..

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